1. Field
Embodiments described herein generally relate to a gasifier and methods for operating the gasifier. More particularly, such embodiments relate to reducing the temperature within the gasifier at one or more locations where oxidant is introduced thereto.
2. Description of the Related Art
Gasification is a high-temperature process that converts carbon-containing feedstocks into mostly gaseous mixtures, including carbon monoxide, carbon dioxide, and hydrogen. The gaseous product is typically referred to as synthesis gas or, more succinctly, syngas. Syngas can be used as a source of hydrogen, for the production of other organic chemicals, and/or to generate steam and/or electricity. Thus, gasification adds value to otherwise low-value feedstocks by converting them to marketable products.
Gasifiers include a riser configured to convert a feedstock and an oxidant into syngas. Heat is generated at the point where the oxidant enters the riser. This generated heat causes a localized hot zone or region having a temperature that can result in structural stresses within the gasifier. To reduce the temperature at the oxidant entry point steam is oftentimes introduced at the entry point with the oxidant, either mixed with the oxidant or independent the oxidant. Due to the already high temperature, e.g., above 100° C., the cooling effects of the steam are limited.
Ash circulating within the riser can also reduce the temperature at the oxidant entry point via heat absorption. When the ash absorbs this additional heat, however, the ash tends to soften, and as the ash softens, it can agglomerate and cause blockages or obstructions within the gasifier.
There is a need, therefore, for improved systems and methods for reducing the temperature at localized hot zones within a gasifier.